The contact arms of a switchgear circuit breaker are used to connect the circuit breaker to the contacts of a circuit breaker truck assembly. The contact arms normally include annular rings disposed in spaced relation for convective heat rejection. These rings are typically of the same outer diameter, maximized to pass ANSI Heat Rise test requirements. These constant diameter rings may cause problems with ANSI BIL (Basic Impulse Level) testing requirements and may force the use of current transformers with Mylar® liners and polycarbonate barriers to prevent flashover to grounded surfaces and equipment. The constant diameter rings may cause high electrostatic field stresses and shorter flashover path lengths to grounded objects in the final switchgear assembly.
In additional, the contact area of high amperage circuit breakers and switchgear contact fingers are a source of heat and temperature rise test failures.
Thus, there is a need to provide improved annular rings on a contact arm and to provide improved contact fingers for convective heat rejection.